Painless Flutter Embedding in Your Existing App

00:01

okay hi everyone uh

00:03

welcome to drakkon online multi-platform

00:06

series and

00:07

my name is hayden hammond and i'm going

00:09

to talk about

00:10

painless flutter embedding in your

00:12

existing app

00:16

a bit about myself i'm from the

00:19

netherlands i am

00:20

a mobile app developer at philips hue

00:23

and i work with flutter since 2018

00:26

within philipsview we launched two apps

00:29

that are built in natively

00:31

or from scratching flutter those were

00:33

are the

00:34

the philips hue bluetooth tab and the

00:36

philips hue sync app

00:38

furthermore i am maintainer of the

00:40

flutter reactive ble

00:42

library which is a library that

00:43

maintains multiple bluetooth connections

00:46

in flutter i'm a sports fanatic

00:49

and i'm stand tree certified which means

00:51

i know myself about wines

00:55

i'm really looking forward to connect to

00:56

you so feel free to reach out on me

00:58

on either twitter or linkedin

01:05

yeah so let's get started a bit about

01:08

flitter

01:08

well everybody did hear about it but

01:11

just for completeness feather is

01:13

google's ui toolkit on which you can

01:16

build multiple natively compiled

01:21

applications on the from a single code

01:23

base if you

01:24

yeah just want to start with litter i

01:27

really urge you to check out

01:28

their website they have really great

01:30

resources

01:32

and also great tutorials the website is

01:35

below

01:39

a bit about the technical overview of

01:42

flutter because that gives also a good

01:45

um

01:46

yeah overview of how the embedding

01:48

actually

01:49

works so first of all we have the oh

01:53

the framework layer which consists of

01:56

the widgets

01:57

where you can define your animations and

01:59

everything in there is written in the

02:01

dart programming

02:02

language and actually dart is a language

02:05

that is introduced by

02:09

um or by google and yeah net

02:12

as flitter as well the next part is the

02:15

engine

02:16

which is built in c and c plus and what

02:19

it is doing for us

02:20

is actually making sure that the frames

02:24

that you created in flutter are properly

02:26

scheduled in the correct sequence

02:27

and also that the data

02:30

is that you yeah that is sent from

02:34

twitter towards the platform is actually

02:37

arriving

02:38

well and that brings me also to the next

02:41

part

02:41

because that's the embedder as you can

02:44

probably imagine

02:45

is that each platform has its own

02:48

treading mechanism and also a different

02:50

way of rendering things

02:52

so that's why that each flutter

02:56

each platform has its own flutter

02:58

embedder for that

03:00

also check out the link that i provided

03:03

below that will give you also a bit more

03:05

background information on it

03:10

now let's get started where we all come

03:11

from the add to app approach

03:15

actually of course what i already

03:17

mentioned the two apps

03:18

that i started with on flutter they were

03:20

greenfield projects which is

03:22

quite a luxury because we could start

03:25

with flutter from scratch but of course

03:29

we all have legacy apps and if we want

03:32

to get started with flutter yeah then

03:34

without the add to app approach we need

03:36

to choose to really rewrite everything

03:38

and that's something we ideally wouldn't

03:40

like to do

03:41

so because of that they introduced

03:45

this approach and what it's actually

03:46

doing is

03:48

you can create a flitter module and

03:51

you can embed it into your existing code

03:53

base and it will

03:55

run seamlessly in your existing apk

03:59

it works for both ios and android

04:02

i'm an android developer so the only

04:05

thing what i can say about ios is that i

04:07

saw working examples of

04:08

it how it works roughly is that

04:11

on ios you can link it together with

04:14

cocoapods

04:15

or embed the framework into xcode

04:20

and since yeah flutter version 1.12

04:24

the adobe approach is has become pretty

04:26

solid if

04:27

someone tried it before that version

04:30

yeah

04:30

it was a bit more difficult but since

04:33

version 1.12 they have

04:34

really nice plugin structure and also

04:36

great embedding

04:38

which makes your life quite easy

04:43

there are two ways to add a floater

04:46

module into your app

04:48

it is adding the creating the module

04:49

inside your existing codebase

04:51

and link it together this is also the

04:55

thing that i want to show you when i'm

04:57

going into more detail

04:59

the other way is create a separate

05:01

repository and then

05:03

build build it an aar and then integrate

05:06

it into your existing app

05:09

what it is doing is you need to run a

05:11

flip of build command build ar

05:14

it will build a kind of

05:17

maven repository and what you need to do

05:19

then is

05:20

you need to make sure that the maven

05:22

repository is uploaded somewhere

05:24

in for example an artifactory or a

05:27

location that makes sense to you where

05:28

you can easily access it

05:30

and what you then do is integrate it

05:33

into your

05:33

gradle build if you run the commands

05:37

they also provide really nice

05:38

output how to do it it's quite simple

05:43

i decided to create an example app

05:47

comfort food app i am really big fan of

05:49

pizzas and burgers so

05:51

i was really happy to make a nice app

05:53

for that and

05:55

actually i explained a bit about the

05:57

structure so what you see on the left

05:59

is the launch screen where you can

06:01

select

06:03

to restaurants and you can

06:06

in the middle you see a pizza screen

06:08

where you can decide okay which size it

06:10

is

06:10

and it will change the price and that

06:14

pizza is a separate android module in my

06:17

app

06:18

and also the the third screen is

06:21

the order overview so once you select

06:24

you know

06:24

the burger or the pizza you want you

06:27

press ok

06:28

and then you can decide to complete the

06:30

order and then you get a nice overview

06:32

with the total price

06:34

also on the right you see the my new

06:35

module which is the

06:37

the burger module and this is 100 built

06:40

in flutter

06:43

okay first of all what do we need well

06:45

of course we need the flutter sdk and

06:48

the flutter sdk can be downloaded

06:50

from the flitter website you probably

06:52

guessed that

06:53

of course we need our beloved android

06:55

studio and we need to make sure that we

06:57

install the flutter plugin which is

06:59

available from the marketplace of

07:00

android studio

07:03

and then what we also need is an

07:05

existing android project that actually

07:06

builds

07:11

then because we installed the flutter

07:14

module

07:15

it will provide we can say in android

07:17

studio

07:18

a new module and then flip the module

07:22

and then it provides us a really nice

07:24

wizard which is quite convenient we fill

07:26

in some details

07:27

and what it then does it will provide

07:29

some kind of structure what you actually

07:31

can see

07:32

here i want to highlight some parts of

07:36

the structure out

07:38

first of all this is the android folder

07:40

which is generated

07:42

and it contains a lot of bindings and

07:47

for example it will make sure that it

07:49

can find the

07:50

filter sdk it consists of

07:53

references to some gradle files which

07:56

make sure that you can build your app

07:58

and that your filter module is properly

08:00

bundled

08:03

the next thing is the lib and the test

08:05

folder which consists of your source

08:07

code

08:08

plus your unit tests and widget tests

08:13

and what is very important is the

08:14

patchback yaml file

08:16

and the perspective file contains you

08:18

declare there your dependencies

08:20

and also what you can do is define some

08:23

metadata and

08:24

what is very important for example is

08:26

the name

08:27

and the version of it

08:33

after generating what it does more is

08:35

also it creates a reference to

08:37

the to a flutter project and

08:41

this is very important for the embedding

08:42

because this specific

08:46

project will do a lot of magic underdoot

08:49

especially when we are building the app

08:51

for example what it is doing is it will

08:54

make sure based on the api

08:56

that you have so the processors that you

08:59

support

09:01

it will make sure that it grabs the

09:02

correct fitter engine

09:04

and what it also will do is it will grab

09:06

the dependencies from

09:08

embedding so when you start using the

09:10

filter engine

09:11

or the filter activity which i will talk

09:13

about later

09:14

you don't need to add those dependencies

09:19

to your gradle file but it's already

09:21

there by this project

09:23

another reference what you see on the

09:25

right and this is actually the

09:26

embedding itself it will link

09:30

the module and it will refer to the

09:32

include flutter.groovy

09:34

and that one starts a chain of events

09:37

actually

09:38

because of this approach it also means

09:40

that there is a limitation that you can

09:42

only embed one flutter module

09:45

per app but of course you can

09:50

quite a lot of flexibility where you can

09:52

add multiple screens and i will

09:54

talk about that a bit later

09:57

next what we need to do is of course we

09:59

need to write the application code

10:01

i'm not going to talk a lot about dart

10:04

code

10:05

but you can see here i created the

10:08

screen containing of some text views

10:11

i created a nice checkbox some image

10:14

and of course some calculation that

10:17

updates the price when we add fries to

10:18

our burger

10:20

and when we click on ok what it actually

10:23

is doing

10:24

it will close the app and it will return

10:26

back to android

10:29

also what is quite convenient is that

10:30

you can run the flutter app

10:32

independently on the phone and that

10:34

helps in the beginning because you

10:36

probably don't want to start with

10:38

embedding until you

10:39

know for sure it actually works so what

10:42

you need to do is you

10:43

need to run the main dart file

10:49

okay then of course

10:52

we have some screen that we can

10:54

integrate and what we need to do next is

10:56

actually integrate the flutter activity

11:02

i chose to use a photo activity for the

11:04

end dabbing

11:05

but there are also other ways to embed

11:07

flutter for example you can embed it

11:09

through a fragment

11:10

and to refer to view but the flutter

11:13

activity is actually

11:14

the easiest way to integrate an embed

11:17

flipper because it provides us

11:19

it does a lot of work for us and also it

11:22

handles a lot of

11:23

life cycle events also what what you can

11:27

do

11:27

for example in a flutter activity is a

11:30

display

11:31

a splash screen you can also define

11:34

a different dart file to run the entry

11:37

point

11:38

or you can choose a different

11:41

route and routes are in flutter ways of

11:44

navigating through the app so if you

11:45

want to

11:47

start a separate part of the app you can

11:49

use a route for that

11:51

and also when you start embedding you

11:53

can say okay i want to run

11:55

flutter and execute this specific route

11:59

what i already mentioned if you're a big

12:01

fan of the one activity approach you can

12:04

use

12:04

the flutter fragment but you need to be

12:06

aware that you need to be

12:08

need to forward some a couple of calls

12:12

and for example a couple of calls that

12:14

you need to um

12:16

forward is on post resume and on

12:19

backpressed

12:20

and a couple of more so

12:23

yeah flutter activity is much easier

12:26

in that regard and actually

12:31

then the only thing what we need to do

12:33

is i have a

12:34

card what i say okay i have a filter

12:37

activity

12:38

i create a default intent and

12:40

[Music]

12:43

i will start it and then i want to give

12:46

a demo

12:52

so let's see how it looks

12:56

so i have my app and i press on the

12:59

burgers

13:02

and it starts but i will do it again

13:05

because probably what you already notice

13:06

is when i tap

13:08

mike's burgers it you see a screen a

13:11

black screen for around

13:12

two seconds and as you can see before it

13:16

actually loads so now we go back

13:22

so it's awesome but it is for user

13:24

experience it's not really fast

13:26

because yeah it feels a bit slow right

13:30

let me explain a bit to you what

13:32

happened so when

13:34

we created the default intent in the

13:36

flutter activity

13:38

what the activity does for us it will

13:40

create a new

13:41

filter engine for us it will

13:44

create gni bindings it will also

13:47

initialize

13:48

our app that we created

13:51

and it will execute the default route

13:53

that we have

13:54

and as you can imagine that takes a

13:56

couple of seconds

13:57

before everything is wired up and that's

13:59

also what you saw

14:03

if only we could make it faster well you

14:06

probably guessed it we definitely can

14:08

because the threader team introduced

14:13

the the concept of a warm-up flutter

14:15

engine

14:16

and i think it makes sense to speed it

14:18

up and

14:19

warm this engine up

14:22

first of all what we need to do is

14:26

we need to create an id for it

14:30

and that id is not for the engine itself

14:32

but it's

14:34

for the cache so it can be found because

14:36

later we need to ask to the cache okay

14:38

give us a specific flutter engine

14:43

then of course we create the flutter

14:45

engine

14:46

and um i want to talk a bit about what

14:49

the filter engine is because a flutter

14:50

engine

14:51

you can see it as a kind of a container

14:54

in through which you can run flitter

14:57

code

14:57

and dart code into your android

15:00

application

15:02

and what you also see in the second line

15:06

is um

15:10

yeah the second line below the creating

15:12

of the flutter engine you will actually

15:13

do the warm up because if you just

15:16

create the flitter engine it doesn't do

15:18

anything

15:18

yet but if you say to the dart executor

15:22

of the flutter engine

15:24

create a cert execute a certain dart

15:26

entry point then it will actually start

15:29

warming up this also means that

15:33

it will start consuming memory and you

15:34

need to pay the

15:36

yeah you need to pay the resources that

15:38

will cost to wire it up

15:42

last but not least what we need to do of

15:44

course is we need to put it in the

15:46

engine cache

15:46

and that's quite simple it's a singleton

15:49

that we can

15:50

retrieve and we just say to the instance

15:54

okay

15:54

we added here with the corresponding id

15:58

so this is what we had before

16:02

and this is what we have now so what we

16:06

are doing is we say to the filter

16:08

activity instead of creating a default

16:10

intent

16:10

we now say

16:13

use a cached engine from the cache and

16:16

then of course we built an intent and we

16:21

started

16:22

so let's see how that looks

16:29

i press now my burgers and as you can

16:32

see it is really fast

16:34

at this moment i will do it again

16:37

to be sure and as you can see it is

16:40

instantly

16:45

so this is pretty awesome

16:49

because now we have the user experience

16:51

that we want the screen is wired up

16:53

nicely

16:54

the only thing what we now need to do is

16:56

of course

16:58

make sure that the data is there

17:01

some attention points by using the

17:04

warmed up engine

17:06

because of course it comes with a price

17:08

that we need to be aware of

17:11

when you pre-one the dart code it means

17:14

that it begins

17:15

begins executing immediately so it also

17:18

means that

17:21

yeah it starts with memory consuming

17:23

memory and also executing some yeah

17:26

the code that you defined in your entry

17:28

point

17:30

also what you need to make sure of is

17:32

that

17:33

when you want to free up the resources

17:35

you call flutter engine.destroy because

17:38

it outlives your flutter activity or

17:40

flood the fragment

17:43

of course what i said is there are

17:45

performance implications

17:47

and i saw on the flitter website they

17:50

have

17:51

put some numbers it was based on version

17:54

1.10

17:55

we are now at 1.7 team um so they are a

17:58

bit outdated but it gives you at least

18:00

some indication um you you need to think

18:03

of that

18:04

wiring up a flitter engine costs 34

18:07

42 mb memory

18:11

and also when you say when you start

18:14

warming up

18:15

there is a blocking call to the ui

18:17

thread of 330 milliseconds

18:21

so that's important to to notice

18:26

also what you need to do is you need to

18:28

make sure that when you start warming up

18:30

you choose already the correct

18:32

dart entry point and also the correct

18:35

flutter out you cannot change it

18:37

afterwards

18:40

and last but not least if the fritter

18:42

activity is the first activity that you

18:44

want to show

18:44

on startup um yeah

18:48

warming up doesn't really make sense

18:50

because yeah you need to

18:52

wait for everything to start at the

18:55

beginning

18:57

the last thing that we need to do is of

18:59

course sending the data

19:01

and what we need to use for that is

19:04

method channels

19:05

and what are those so you can see

19:07

there's indeed a name channel that

19:09

sends data between the flutter client

19:11

and the native host

19:14

that's the way approach i used for

19:17

disembedding but you can also do it the

19:19

other way around so

19:20

pretty can also be the host and native

19:24

can be the client

19:29

messages and responses are always passed

19:31

asynchronously

19:32

you can make sure that from the host

19:34

that you provide the correct callback so

19:36

the client can

19:37

handle on either the error or the

19:40

success that you

19:41

have and this is very important for

19:46

android users because when you start

19:48

using

19:49

flutter you want actually to

19:53

execute some background processing for

19:55

example bluetooth

19:56

or databases you need to execute it

19:59

natively

20:00

and of course if you do that yeah the

20:04

work there is

20:04

handled on the background thread but if

20:07

you

20:08

want to give a call back towards

20:11

flitter again you need to make sure that

20:13

you invoke that callback on the main

20:15

thread

20:15

of android the same counts

20:18

when you are using streams and you want

20:22

to

20:22

send data you need to make sure that

20:24

it's provided also on the main thread

20:26

there

20:29

a bit of architectural view that

20:32

that will give you some explanation

20:34

about my implementation

20:37

first of course i want to invoke a

20:38

method complete order

20:40

from the flutter client and

20:43

i provide some arguments at some point

20:47

android starts processing it

20:49

checking some things and it will provide

20:52

be

20:52

a success

20:56

how does it look on the flip side what

20:57

we need to do

20:60

first we need to create the method

21:03

channel

21:04

and the name that we create is important

21:06

because this one needs to match also on

21:08

the android side

21:13

then of course what i did is i created

21:15

the kind of simple backend

21:18

i will i invoke the method called

21:21

complete order

21:22

also the string name of the method needs

21:25

to match on the android side

21:27

and i provided some arguments and as you

21:30

can see

21:31

the arguments are a list of dynamic

21:35

and that is because i'm using the

21:38

standard codec for flutter and what that

21:40

one is doing it

21:42

before it will actually send it towards

21:44

native it will

21:45

convert it to binary for me so yeah

21:48

that's why

21:49

i can do this also there's another

21:52

standard codec that is provided and that

21:54

is a json

21:55

codec but for there are also other

21:59

codecs available

22:01

as third party and for example for my

22:03

bluetooth library i'm using protobuf

22:05

protocol

22:07

which provides us a bit more type safety

22:13

okay so we have everything in the on the

22:16

dart side

22:17

and now we need to go back to the

22:18

android side and what we need to do

22:20

first

22:21

is create the meta channel as well with

22:24

the same name

22:27

and now it's actually quite convenient

22:28

that i added the

22:30

flutter engine in my application because

22:32

i can easily access it

22:34

through application context and what we

22:37

need to

22:38

provide if we create a meta channel we

22:40

need to provide the

22:41

nice binary messenger of the flutter

22:44

engine

22:45

and of course the matching name that is

22:47

the same on flutter

22:49

then what we need to do is we need to

22:51

set a method call handler because we are

22:54

the host and we need to handle the

22:56

requests that we get from the flutter

22:58

client

22:59

so let's look how that sees

23:03

we created an automated call handler and

23:07

we override

23:08

the from the embedding the method call

23:10

handler

23:11

that means also we are forced to

23:13

overwrite all method call

23:15

and what you can see here is i first

23:17

check the method name

23:19

if it is invoked with the correct

23:23

complete order string then i will do

23:26

some things but

23:27

if not i will say okay this method is

23:30

not implemented and

23:32

so we can handle on the other side the

23:35

issue

23:37

furthermore of course what you see here

23:39

is also the arguments are

23:41

a list of eddy and we need to make sure

23:44

that

23:45

the types are correctly and if they are

23:48

correctly we

23:49

can do the processing and we report the

23:52

success to flutter

23:54

and if not we report some error that the

23:57

incorrect values

23:58

are supplied

24:01

let's see now the result how does it

24:03

look like

24:06

i tap on mike's burgers well

24:10

let's add some fries as well i press ok

24:15

you see a button below appearing which

24:18

is a good sign already and if i press it

24:22

what you can see here is i get the

24:25

ultimate burger with price for

24:26

10

24:32

so this is really awesome we completed

24:34

everything what we wanted to do now

24:39

but i can imagine i went through it in

24:42

20 minutes

24:43

so i think it's very good to wrap things

24:45

up what we did

24:49

so first of all we created the fritter

24:51

module uh

24:52

using the flutter plugin that we

24:54

installed on android studio

24:56

and added and because of that it wired

24:59

up nicely and it generates

25:01

a lot of things so we can actually embed

25:03

the module

25:05

then of course we created the code and

25:10

then what happens is we

25:13

could launch the flitter module when we

25:14

clicked on the card for mike's burgers

25:18

then what we use what we did is because

25:21

we weren't happy of the user experience

25:23

we used the warm the filter engine

25:26

and last but not least we were able to

25:28

send the data so we can

25:30

provide a nice overview of the order

25:36

some attention points in regards to the

25:39

at the web approach because there are

25:41

some things you need to be aware of

25:44

first of all flitter does not support

25:47

32 bits and mid processors

25:51

so if you want to start with embedding

25:53

flutter you need to make sure that you

25:55

deprecate those processor architectures

25:58

and also

25:59

even more important you need to set the

26:00

correct api filters in

26:02

your gradle file because if you don't do

26:06

it

26:07

and you still have so people that have a

26:10

32 bits

26:11

phone for example can still install your

26:13

app and then it will crash because the

26:15

footer engine for that processor

26:17

architecture cannot be found

26:19

so you yeah that's quite nasty

26:24

also what i read on the documentation is

26:27

that flutter

26:28

in background mode is not fully

26:29

supported already i saw

26:32

they are doing quite some work on it but

26:34

it's still working progress so

26:36

use it at your own risk

26:42

yeah what i already mentioned before is

26:43

you cannot embed

26:45

multiple throttle modules into one

26:47

application

26:49

of course what you can do is you can use

26:51

different

26:52

dart entry points and also what you can

26:55

do is you can

26:56

play around nicely with routes if you

26:58

define your navigation correctly in

26:60

flutter

27:01

you can save from the embedding okay in

27:03

this case i want to

27:05

execute this specific part of my app and

27:07

a bit later i want to execute that

27:09

specific part of my app

27:15

also in flattery it can happen that you

27:17

are using some android plugins

27:19

and that those android plugins are not

27:22

using the latest

27:24

plugin structure what you will see is

27:27

when you compile your app

27:28

it will give you a warning that hey keep

27:31

in mind

27:31

this the the plugin x that you are using

27:35

is using old android plugin structure

27:39

so really yeah make sure that you

27:42

migrate it

27:42

because else we cannot guarantee it work

27:45

it behaves

27:47

nicely

27:50

also and this is quite a no-brainer you

27:52

need specific ci for flutter because the

27:55

ecosystem is totally different

27:56

a different language

28:03

also what is very important is that from

28:07

version 1.17 and this is the latest

28:10

table

28:11

that you you need to make sure that your

28:13

application is migrated

28:15

to android x

28:20

this is a very interesting one because

28:23

both twitter and android they are using

28:25

the material

28:26

design library which is google's

28:29

ui library and what you

28:33

what can happen is that if there are

28:35

some new components in the material

28:36

library

28:37

it can happen that they are present on

28:40

android

28:41

but not in flitter or the other way

28:43

around

28:44

so if you want to use those components

28:47

always make sure that

28:50

they are available in both because you

28:54

ideally would like to have the same ux

28:56

experience on both

28:57

sides also what they say

29:01

we saw a really nice trick like warm up

29:04

the flutter engine

29:05

but of course you cannot do that

29:07

unlimitedly

29:08

actually what they are saying the

29:10

flutter team is saying yeah if you want

29:12

to use multiple filter engines

29:14

you can do it we won't limit it but it

29:17

is at your own risk

29:21

and the last point that i want to

29:22

address is

29:25

that you need to make sure um for

29:27

example if you use

29:28

chrysler x in your floater module and

29:31

use also crashlytics

29:32

in your android what can happen is that

29:35

for example in

29:36

android you use a newer version of

29:39

prosthetics then is available in the

29:41

flutter plugin

29:43

of course what gradle is doing normally

29:45

it resolves the versions

29:46

and it will install the the newest one

29:50

but of course if they are in the api

29:52

some breaking changes

29:54

your flutter implementation will not

29:56

work

29:57

so in that case you need to make sure

29:59

that both presslytics on

30:01

flitter as in android are of the same

30:07

version

30:09

useful resources that i want to share

30:10

with you example

30:12

the basic example that i showed you is

30:14

available on github

30:15

so feel free to look into it

30:18

i'm also planning to add some more

30:21

complicated scenarios for that

30:23

to give a bit more overview

30:26

also really check out the flutter

30:28

website they have

30:29

really good documentation about add to

30:31

app also for ios

30:33

and if you are an android developer and

30:35

you want to get started

30:36

they have a nice starting point that is

30:40

the third

30:40

bullet point and last but not least

30:43

platform channels

30:44

i just scratched the surface on it with

30:47

the meta channel but they are really

30:49

powerful so check them out

30:53

and then i want to thank you for your

30:54

attention i really enjoyed speaking with

30:57

you about android

30:58

vetting and i'm looking forward to

30:60

answer any questions that you have

31:02

thank you very much thanks so much

31:05

everyone it was really fantastic

31:07

um appreciate it appreciate all the tips

31:09

and the resources as well

31:10

let's make we do have a few questions so

31:12

we'll make um

31:13

uh uli the moderator and he'll be able

31:15

to show you what questions have come up

31:16

on slido so it's all

31:18

perfect

31:28

so you should see the screen right now

31:30

and you can feel free to read the

31:32

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